Lidstock laminate for poultry packaging

ABSTRACT

A laminate useful as a lidstock for poultry packaging generally includes a first film capable of bonding directly to a surface comprising foamed polystyrene at a bond strength ranging from about 0.5 to about 5.0 lb f  per inch, a second film bonded to the first film, and a printed image trapped between the first and second films. At least one of the first and second films may have a free shrink at 185° F. in at least one direction of at least about 10%. Further, the laminate may have a gas transmission rate greater than about 3000 cubic centimeters per square meter per day per 1 atmosphere of gas pressure differential measured at 0% relative humidity and 23° C.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a packaging film and, moreparticularly, to a laminate useful as a lidstock for sealing to a foamedpolystyrene tray. The resultant package is advantageously used topackage poultry.

[0002] It is common in food packaging operations for a food product,such as fresh meat, to be placed on a support member, such as athermoformed expanded polystyrene tray having a central depressed areaand a surrounding peripheral flange. A thermoplastic film or laminate istypically then positioned over the food and bonded to the peripheralflange to enclose the food product. In such arrangement, thethermoplastic film or laminate is generally referred to as the “lid” or“lidstock” for the tray or other support member.

[0003] Bonding of the lid to the support member is typicallyaccomplished by effecting a “heat seal” between the lid and supportmember, generally by engaging the outside of the lid with a heated barin the form of a closed geometrical shape corresponding with the shapeof the flange. The bar compresses the lid against the flange. In sodoing, heat transfers from the heated bar to the outside of the lid,through the thickness of the lid, and to the inside sealant layer of thelid and the flange of the support member. The resulting heat andcompression causes the contacting surfaces of the lid and support memberto become molten and to intermix with one another. The heating bar isthen removed to allow the sealed area to cool and form a sealed bond.

[0004] In order to ensure that the packaged food product remains freefrom dust, dirt, moisture, and other external contaminants, it isimportant that the lidstock be capable of forming a strong, hermeticseal with the support member. In the past, it has generally beennecessary to provide a liner on the inner surface of the support memberin order to provide a surface to which the lidstock can be bonded. Thisis because it is difficult to bond lidstock materials directly to thefoamed surface of a support member flange via heat sealing as describedabove. As a result, prior to thermoforming a polystyrene foam sheet intoa tray or other support member, a separate film has typically beenlaminated to a surface of the sheet to form a liner, which is disposedon the inner surface of the support member cavity and upper surface ofthe flange upon thermoforming the sheet into a support member. As mayreadily be appreciated, such a step adds time, complexity, and expenseto the tray manufacturing process, and generally also makes it moredifficult to recycle excess foam sheet that invariably results from theprocess.

[0005] When packaging fresh red meat in packages that comprise a liddedsupport member, a liner has also been generally necessary in order toprovide a sufficient barrier to the ingress of oxygen into the package,since foamed support members themselves typically do not provide asufficient barrier to the passage of oxygen. Such liners would bedisadvantageous for the packaging of poultry, however, in that packagedpoultry produces hydrogen sulfide gas, which has an unpleasant odor thatis very disagreeable to most consumers. Poultry therefore requireshighly gas-permeable packaging material to allow such gas to begradually released from the package, i.e., as it is generated by thepoultry. If the gas is not released from the package in a gradualmanner, it becomes trapped within the package and is then essentiallyreleased all-at-once in the presence of the consumer when the consumeropens the package, much to the displeasure of the consumer. A non-lined,foamed polystryene support member would be ideal for poultry packaging,due to its relatively high degree of gas-permeability and low cost incomparison to a lined support member, provided that a suitable liddingmaterial could be bonded thereto in such a manner as to form a hermeticseal between the lid and support member.

[0006] It is also desirable for the lidstock to be printed. Suchprinting provides important information to the end-user of the packagedfood—information such as the ingredients of the packaged food, thenutritional content, package opening instructions, food handling andpreparation instructions, and food storage instructions. The printingmay also provide a pleasing image and/or trademark or other advertisinginformation to enhance the retail sale of the packaged product. Suchprinted information may be placed on the outside surface of thelidstock. However, such surface printing is directly exposed to a heatedbar during the heat seal operation that seals the lid to the supportmember. As a result, the surface printing may become smeared orotherwise degraded. Surface printing is also exposed to other physicalabuses during distribution and display of the packaged product. Suchabuse may also degrade the clarity and presentation of the printedimage. Means for protecting the printed image is therefore desired.

[0007] Accordingly, there is a need in the art for a lidstock materialthat meets the foregoing requirements for poultry packaging.

SUMMARY OF THE INVENTION

[0008] The present invention addresses one or more of the aforementionedproblems.

[0009] A laminate useful as a lidstock comprises:

[0010] a. a first film capable of bonding directly to a surfacecomprising foamed polystyrene at a bond strength ranging from about 0.5to about 5.0 lb_(f) per inch;

[0011] b. a second film bonded to the first film; and

[0012] c. a printed image trapped between the first and second films,

[0013] wherein:

[0014] at least one of the first and second films has a free shrink at185° F. in at least one direction of at least about 10%, and

[0015] the laminate has a gas transmission rate greater than about 3000cubic centimeters per square meter per day per 1 atmosphere of gaspressure differential measured at 0% relative humidity and 23° C.

[0016] Another aspect of the invention is directed towards a package,comprising:

[0017] a. a product support member for supporting a product thereon, thesupport member comprising foamed polystyrene; and

[0018] b. a laminate, comprising a first film and a second film bondedtogether with a printed image trapped therebetween,

[0019] wherein:

[0020] at least one of the first and second films has a free shrink at185° F. in at least one direction of at least about 10%,

[0021] the laminate has a gas transmission rate greater than about 3000cubic centimeters per square meter per day per 1 atmosphere of gaspressure differential measured at 0% relative humidity and 23° C., and

[0022] the first film is bonded to the support member in the form of apeelable, hermetic seal that extends around the product to enclose theproduct between the laminate and support member, the seal having a bondstrength ranging from about 0.5 to about 5.0 lb_(f) per inch.

[0023] A further aspect of the invention is directed towards a package,comprising:

[0024] a. a product support member for supporting a product thereon, thesupport member having an upper surface consisting essentially of foamedpolystyrene; and

[0025] b. a film bonded directly to the upper surface of the supportmember in the form of a peelable, hermetic seal that extends around theproduct to enclose the product between the film and support member, theseal having a bond strength ranging from about 0.5 to about 5.0 lb_(f)per inch, the film having a free shrink at 185° F. in at least onedirection of at least about 10% and a gas transmission rate greater thanabout 3000 cubic centimeters per square meter per day per 1 atmosphereof gas pressure differential measured at 0% relative humidity and 23° C.

[0026] Yet another aspect of the invention pertains to a package,comprising:

[0027] a. a product support member for supporting a product thereon; and

[0028] b. a laminate, comprising a first film and a second film bondedtogether,

[0029] wherein:

[0030] the first film is bonded to a surface of the support member inthe form of a peripheral seal that extends around the product to enclosethe product between the film and support member, and

[0031] the second film is cross-linked to a greater degree relative tothe first film such that the second film has a melt flow index of lessthan about 1.0 g/10 min. and the first film has a melt flow index ofgreater than about 1.0 g/10 min.

[0032] The foregoing laminates and packages made therefrom are ideallysuited for poultry packaging. The laminates have a sufficiently highdegree of permeability to allow the hydrogen sulfide produced bypackaged poultry to gradually permeate out of the package. Further, thelaminates can bond directly to foamed polystyrene with a hermetic,peelable heat-seal so that a non-lined, foamed polystyrene tray may beused, which adds further permeability to the package and is easier andless costly to manufacture than a tray having a film liner. Thelaminates are also heat-shrinkable, thereby forming a tight,aesthetically-pleasing lid for the package as a result of beingheat-sealed to the tray. Moreover, the laminates can accommodate atrap-printed image between the first and second films, therebyprotecting the image from degradation during distribution and display.

[0033] These and other objects, advantages, and features of theinvention will be more readily understood and appreciated by referenceto the detailed description of the invention and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0034]FIG. 1 is a perspective view of the sealed package of the presentinvention; and

[0035]FIG. 2 is a fragmentary, representational sectional view of theinventive laminate and sealed package of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0036] The inventive laminate 10 comprises a first, sealant film 12laminated to a second, heat-resistant film 14. A printed image 16 ispreferably trapped between the first and second films 12 and 14. Firstfilm 12 may be monolayer, two-layer, or have three or more layers (asshown in FIG. 2). Also, second film 14 may be monolayer, two-layer, orhave three or more layers (as shown in FIG. 2). The laminate 10 may besealed to support member 18 (e.g., a tray as shown) to form sealedpackage 20 enclosing food product 22, e.g., a poultry product such aschicken, turkey, cornish hen, pheasant, duck, etc.

First, Sealant Film

[0037] The sealant film 12 defines an inside (i.e., food side) surface24 and an outside surface 26 opposite the inside surface. The polymermaterial (i.e., component or blend of components) that forms the insidesurface 24 of the sealant film has a melting point and appropriatechemical characteristics to facilitate heat sealing laminate 10 tosupport member 18. If the sealant film is monolayer, then it may havethe composition, attributes, and physical characteristics as discussedin conjunction with the Sealant Layer section below.

[0038] The sealant film 12 may have any total thickness as long as itprovides the desired properties (e.g., permeability, flexibility,Young's modulus, optics, strength) for the given packaging applicationof expected use. The sealant film may have a thickness of less thanabout any of the following: 10 mils, 5 mils, 4 mils, 3 mils, 2 mils, 1.5mils, 1.4 mils, 1.3 mils, 1.2 mils, 1.1 mils, and 1 mil. (A “mil” isequal to 0.001 inch.) The sealant film may also have a thickness of atleast about any of the following: 0.3 mils, 0.4 mils, 0.5 mils, 0.6mils, 0.7 mils, 0.75 mils, 0.8 mils, 0.9 mils, 1 mil, 1.2 mil, 1.4 mil,and 1.5 mil. The thickness of the sealant film may be greater than,equal to, or less than the thickness of the second, heat-resistant film14.

[0039] The sealant film 12 preferably has a gas transmission rate of atleast about any of the following: 5,000, 10,000, 15,000, 20,000, and50,000 cubic centimeters per square meter per day per 1 atmosphere ofgas pressure differential measured at 0% relative humidity and 23° C.,measured according to ASTM D-3985.

[0040] The sealant film 12 may be heat-shrinkable so that, upon beingheat-sealed to support member 18, the resultant heat exposure will causethe film to tighten as it attempts to shrink while being bonded to thesupport member. Such tightening produces an aesthetically appealingpackaging appearance. The sealant film 12 may have a free shrink in atleast one direction (i.e., machine or transverse direction) or in atleast each of two directions (machine and transverse directions),measured at 185° F., of at least about 10%, such as at least about 15%,20%, 25%, 302%, 40%, 50%, 55%, 60%, or 65%. Further, the sealant filmmay have a free shrink in at least one direction (machine or transversedirection) or in at least each of two directions (machine and transversedirections) of at least about any of the foregoing shrink values whenmeasured at any of 185° F., 190° F., 200° F., or 210° F.

[0041] As is known in the art, the total free shrink is determined bysumming the percent free shrink in the machine (longitudinal) directionwith the percentage of free shrink in the transverse direction. Forexample, a film which exhibits 50% free shrink in the transversedirection and 40% free shrink in the machine direction has a total freeshrink of 90%. Although preferred, it is not required that the film haveshrinkage in both directions. Unless otherwise indicated, each referenceto free shrink in this application means a free shrink determined bymeasuring the percent dimensional change in a 10 cm×10 cm specimen whensubjected to selected heat (i.e., at a certain temperature exposure)according to ASTM D 2732. Also, a reference herein to the shrinkattributes of a film that is a component of a laminate refers to theshrink attributes of the film itself, which can be measured byseparating the film from the laminate.

[0042] The sealant or first film 12 is preferably multilayer (i.e.,includes two or more layers) so that the layers in combination impartthe desired performance characteristics to the sealant film. The sealantfilm 12 may, for example, comprise from 2 to 15 layers, at least 3layers, at least 4 layers, at least 5 layers, from 2 to 4 layers, from 2to 5 layers, or from 5 to 9 layers. As used herein, the term “layer”refers to a discrete film component which is coextensive with the filmand has a substantially uniform composition.

[0043] A multilayer sealant film includes a sealant layer 28 forming thefood-side or inside surface 24 and a outer or print-side layer 30forming the outside or non-food surface 26 of the sealant film. Themultilayer sealant film may also include one or more additional layers32, such as core, bulk, and tie layers.

[0044] Below are some examples of multilayer film combinations in whichthe alphabetical symbols designate the resin layers. Where themultilayer sealant film representation below includes the same lettermore than once, each occurrence of the letter may represent the samecomposition or a different composition within the class that performs asimilar function.

[0045] A/D, A/C/D, A/B/D, A/B/C/D, A/C/B/D, A/B/B/D, A/C/B/C/D,A/B/B/B/D, A/B/C/B/D, A/C/B/B/D, A/C/B/B/C/D, A/B/C/B/C/D, A/C/B/C/B/D,A/B/C/B/B/D, A/C/B/B/B/D, A/C/B/C/B/D, A/C/B/B/B/C/D

[0046] “A” is the sealant layer (heat seal layer), as discussed below.

[0047] “B” is a core or bulk layer, as discussed below.

[0048] “C” is a tie layer, as discussed below.

[0049] “D” is an outer or print-side layer, as discussed below.

Sealant Layer of the Sealant Film

[0050] Sealant layer 28 forms the inside surface 24 of the laminate 10.Sealant layer 28 facilitates the heat-sealing of laminate 10 to anotherobject, such as support member tray 18. Preferably, sealant layer 28includes selected components that are capable of bonding directly to asurface comprising or consisting essentially of foamed polystyrene,e.g., a support member such as 18 formed from foamed polystyrene andhaving no film or “liner” on the inner or upper sealing surfaces thereofto facilitate bonding. More preferably, sealant layer 28 of the first,sealant film 12 is capable of bonding to a foamed polystyrene surface inthe form of a heat-seal, e.g., a peripheral heat-seal between thesealant film and a flanged support member as described above. Asdiscussed in further detail below, such heat-seal is more preferably apeelable, hermetic seal, i.e., one that maintains seal integrity duringpackaging, transportation, and placement in a retail display case forconsumer purchase, but which can be conveniently opened via peeling bythe consumer just prior to cooking the packaged food product 22. It hasbeen discovered that a peelable, hermetic seal between the sealant filmand a foamed surface may be achieved when the bond-strength therebetweenranges from about 0.5 to about 5.0 lb_(f)/inch of film width.

[0051] When support member 18 is formed from foamed polystyrene orsimilar materials, a bond-strength that falls within the desired rangeof 0.5 to 5.0 lb_(f)/inch may be achieved when sealant layer 28 includesone or more copolymers or terpolymers comprising a styrenic componentand a rubbery component, wherein the rubbery component has at least one,carbon-carbon double bond and comprises no more than about 50 wt. % ofthe thermoplastic elastomer. Preferred materials comprise a blockcopolymer or terpolymer, wherein the rubbery component is distributed inthe copolymer or terpolymer between styrenic end-blocks. Preferredexamples of such block copolymers or terpolymers that are useful inaccordance with the present invention include the following:styrene-ethylene-butylene-styrene block copolymer (SEBS),styrene-butadiene-styrene block copolymer (SBS), andstyrene-isoprene-styrene block copolymer (SIS). As an alternative toblock copolymers and terpolymers, random copolymers and terpolymerscomprising styrene and a rubbery component may be employed, such aspolybutadiene/styrene rubber.

[0052] Other materials that may be employed in sealant layer 28 includepolystyrene (PS); blends of PS and elastomers, such as, e.g.,polybutadiene rubber, butyl rubber, polychloroprene rubber,acrylonitrile-butadiene rubber, vinylpyridine rubber, ethylene-propylenerubber, etc.; ethylene/vinyl acetate copolymer, particularly thosehaving a vinyl acetate content of at least about 15 weight percent; andethylene/methyl acrylate coplymer.

[0053] The sealant layer 28 may have a composition such that any one ofthe above described polymers comprises at least about any of thefollowing weight percent values: 30, 40, 45, 50, 55, 60, 65, 70, 75, 80,85, 90, 95, and 100% by weight of the layer.

[0054] The thickness of the sealant layer is selected to providesufficient material to effect a strong heat seal bond, yet not so thickso as to negatively affect the gas-permeability of the sealant film bydecreasing such permeability to an unacceptable level. The sealant layermay have a thickness of at least about any of the following values:0.01, 0.02, 0.025 mils, 0.05 mils, 0.1 mils, 0.15 mils, 0.2 mils, 0.25mils, 0.3 mils, 0.35 mils, 0.4 mils, 0.45 mils, 0.5 mils, and 0.6 mils.For example, the sealant layer may have a thickness ranging from about0.025 to about 1 mil, from about 0.025 to about 0.6 mils, or from about0.05 to about 0.3 mils. Further, the thickness of the sealant layer as apercentage of the total thickness of the sealant film 12 may range,e.g., from about 1 to about 50 percent, from about 5 to about 45percent, from about 10 to about 45 percent, from about 15 to about 40percent, from about 15 to about 35 percent, or from about 15 to about 30percent.

Outside, Interface Layer of the Sealant Film

[0055] The outside, interface layer 30 of sealant film 12 may providethe surface upon which a printed image (e.g., printed information) isapplied, in which case the layer is preferably capable of providing asurface that is compatible with the selected print ink system. Further,the outside layer 30 provides the outside surface 26 that interfaceswith second film 14 and to which the second film 14 is directlylaminated, as discussed in more detail below.

[0056] The outside layer 30 may include any of the thermoplastics orcompositions as discussed above in conjunction with the sealant layer28. The outside layer 30 may have a composition or thickness (or both)substantially similar to the sealant layer 28. Preferred polymers foroutside layer 30 include one or more of the following: styrenic-basedcopolymers, terpolymers, and blends as described above with respect tosealant layer 28, heterogeneous (Zeigler-Natta catalyzed)ethylene/alpha-olefin copolymers such as linear low densitypolyethylene, homogeneous (single-site, metallocene-catalyzed)ethylene/alpha-olefin copolymers, polyethylene homopolymers (LDPE orHDPE), polypropylene homopolymers, polypropylene copolymers such aspropylene/ethylene copolymer, polyamides, copolyamides, polyesters, andcopolyesters, either alone or in combination. The outside layer 30 mayhave a composition such that any one of the above-described polymerscomprises at least about any of the following weight percent values: 30,40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, and 100% by weight ofthe layer.

[0057] The outside layer 30 may have a thickness of from about 0.025 toabout 1 mil, such as from about 0.025 to about 0.6 mil or from about0.05 to about 0.3 mil. The thickness of the outer layer may range as apercentage of the total thickness of the sealant film of, e.g., fromabout 1 to 50 percent, 3 to 45 percent, 5 to 40 percent, 7 to 35percent, or 7 to 30 percent. Useful thicknesses for the outer layerinclude at least about any of the following values: 0.025 mil, 0.05 ml,0.1 mil, 0.15 mil, 0.2 mil, and 0.25 mil.

Additional Layers of the Sealant Film

[0058] The sealant film 12 may include one or more additional layers 32,such as a tie, core, or bulk layers. A tie layer is an inner film layerhaving the primary purpose of adhering two layers of a film together.The tie layers, if present in the sealant film, may have the compositionand other attributes as described below in conjunction with the tielayers that may also be used in second film 14.

[0059] A core or bulk layer may be an inner film layer having a primarypurpose other than as a tie layer—for example, serving to provide amultilayer film with a desired level of strength, modulus, or optics. Acore or bulk layer may include one or more of the polymers and/or have acomposition as described above with respect to the sealant layer 28and/or outer layer 30.

[0060] Each of the additional layers 32 may have a thickness of fromabout 0.05 to about 5 mils, such as from about 0.1 to about 2 mils orfrom about 0.2 to about 0.5 mils. The thickness of an additional layermay range as a percentage of the total thickness of the sealant film of,e.g., from about 1 to 80 percent, 3 to 50 percent, 5 to 40 percent, 7 to35 percent, or 7 to 30 percent. Preferably, adjacent film layers havedifferent compositions.

Second, Heat-Resistant Film

[0061] The second, heat-resistant film 14 defines an inside surface 34and an outside surface 36 opposite the inside surface. The outsidesurface 36 of the heat-resistant film 14 forms the surface that mayengage the heated bar of a heat-sealing device (not shown) used insealing laminate 10 to support member 18, as discussed in more detailbelow. The outside layer 40 forms the outside surface 36 of theheat-resistant film.

[0062] The heat-resistant film 14 may have any total thickness as longas it provides the desired properties (e.g., permeability, flexibility,Young's modulus, optics, strength) for the given packaging applicationof expected use. The heat-resistant film may have a thickness of lessthan about any of the following: 10 mils, 5 mils, 4 mils, 3 mils, 2mils, 1.5 mils, 1.2 mils, and 1.1 mils. The heat-resistant film may alsohave a thickness of at least about any of the following: 0.2 mils, 0.25mils, 0.3 mils, 0.35 mils, 0.4 mils, 0.45 mils, 0.5 mils, 0.6 mils, 0.75mils, 0.8 mils, 0.9 mils, 1 mil, 1.2 mils, 1.4 mils, and 1.5 mils.

[0063] The heat-resistant film 14 preferably has a construction thatenables the film to withstand the heat transferred thereto from theheated bar of a heat-seal device during heat-sealing/packagingoperations. Such construction also preferably provides the film withabuse- and impact-resistance. With these attributes, the heat-resistantfilm 14 thus provides protection to the laminate during packaging,shipment, storage, and customer inspection at retail.

[0064] Heat-resistant film 14 preferably has a gas transmission rate ofat least about any of the following: 5,000, 10,000, 15,000, 20,000, and50,000 cubic centimeters per square meter per day per 1 atmosphere ofgas pressure differential measured at 0% relative humidity and 23° C.,measured according to ASTM D-3985.

[0065] The heat-resistant film 14 may be heat-shrinkable so that, uponbeing heat-sealed to support member 18, the resultant heat exposure willcause the film to tighten as it attempts to shrink while being bonded tothe support member. Such tightening produces an aesthetically appealingpackaging appearance. The heat-shrinkability of the film 14 may begreater than, the same as, or lesser than that of sealant film 12.Heat-resistant film 14 may have a free shrink in at least one direction(i.e., machine or transverse direction) or in at least each of twodirections (machine and transverse directions), measured at 185° F., ofat least about 10%, such as at least about 15%, 20%, 25%, 30%, 40%, 50%,55%, 60%, or 65%. Further, the sealant film may have a free shrink in atleast one direction (machine or transverse direction) or in at leasteach of two directions (machine and transverse directions) of at leastabout any of the foregoing shrink values when measured at any of 185°F., 190° F., 200° F., or 210° F.

[0066] The heat-resistant or second film 14 is preferably multilayer sothat the layers in combination impart the desired performancecharacteristics to the heat-resistant film. The heat-resistant film 14may comprise multiple layers, for example 2 layers, from 2 to 15 layers,3 layers, at least 3 layers, at least 4 layers, at least 5 layers, from2 to 4 layers, from 2 to 5 layers, and from 5 to 9 layers.

[0067] A multilayer heat-resistant film includes: i) an inside,interface layer 38 forming the inside surface 34 of the heat-resistantfilm and which, upon lamination, interfaces with and is bonded to theoutside layer 30 of the sealant film 12, and ii) a heat-resistant,outside layer 40 forming the outside surface 36 of the heat-resistantfilm 14. The inside layer 38 may be directly adhered to the outsidelayer 40. Alternatively, one or more inner layers 42, such as tie, core,and bulk layers, may exist between the inside layer 38 and the outsidelayer 40.

[0068] Below are some examples of layer combinations for the multiplelayer heat-resistant film 14 in which the alphabetical symbols designatethe resin layers. Where the multilayer heat-resistant filmrepresentation below includes the same letter more than once, eachoccurrence of the letter may represent the same composition or adifferent composition within the class that performs a similar function.

[0069] E/F, E/C/F, E/B/F, E/C/B/F, E/B/C/F, E/C/B/C/F

[0070] “B” is a core or bulk layer, as discussed above with respect tothe sealant film.

[0071] “C” is a tie layer, as discussed below.

[0072] “E” is the inside layer of the heat-resistant film, as discussedbelow.

[0073] “F” is an outside or heat-resistant layer of the heat-resistantfilm, as discussed below.

Heat-Resistant Layer of the Heat-Resistant Film

[0074] During heat-sealing, the outside, heat-resistant layer 40 will bedirectly exposed to the heat seal bar of the heat-sealing equipment (notshown) when forming the sealed package 20. Thus, the outside layer 40preferably provides heat-resistant characteristics to second film 14(and laminate 10) to help prevent “burn-through” during heat sealing.This is because in forming package 20 by conductive heat-sealing of thelaminate 10 to support member 18, sealant layer 28 is placed in contactwith the support member 18, while the outside layer 40 is proximate theheated bar of the heat sealing apparatus. The heat seal bar transfersheat through the outside layer 40, through laminate 10, and to thesealant layer 28 to form a heat seal 44 between the laminate and supportmember 18. Accordingly, outside layer 40 may be exposed to the highesttemperature during the sealing operation.

[0075] The heat-resistant film 14 may also be exposed to environmentalstresses, for example once the heat-resistant film is incorporated intolaminate 10 and formed into a package 20. Such environmental stressesinclude abrasion and other abuse during processing and shipment. Thus,the outside layer 40 preferably provides enhanced resistance to abuse.

[0076] The outside layer 40 may include one or more of any of thefollowing: polyolefins (e.g., polyethylenes, polypropylenes),polyamides, polyesters, polystyrenes, polyurethanes, and polycarbonates.In order to provide high gas-permeability, however, outside layer 40preferably comprises one or more polyolefins, polystyrenes, orpolyurethanes. For example, layer 40 may include any of these polymersin an amount of at least 50 weight %, more preferably at least 70%,still more preferably at least 90%, and most preferably 100% by weightof the layer.

[0077] The outside layer 40 may have a thickness of from about 0.025 toabout 1.25 mils, such as from about 0.05 to about 0.6 mil or from about0.1 to about 0.3 mil. The thickness of the outside layer may range as apercentage of the total thickness of the heat-resistant film, e.g., fromabout 1 to 50 percent, 3 to 45 percent, 5 to 40 percent, 7 to 35percent, or 7 to 30 percent. Useful thicknesses for the outside layerinclude at least about any of the following values: 0.05 mils, 0.1 mils,0.15 mils, 0.2 mils, 0.25 mils, 0.3 mils, 0.35 mils, and 0.4 mils.

Tie Layers of the Sealant and/or Heat-Resistant Film

[0078] The heat-resistant film 14 and/or sealant film 12 may include oneor more tie layers, which have the primary purpose of improving theadherence of two layers of a film to each other. Tie layers may includepolymers having grafted polar groups so that the polymer is capable ofcovalently bonding to polar polymers. Useful polymers for tie layersinclude ethylene/unsaturated acid copolymer, ethylene/unsaturated estercopolymer, anhydride-modified polyolefin, polyurethane, and mixturesthereof. Preferred polymers for tie layers include one or more ofethylene/vinyl acetate copolymer having a vinyl acetate content of atleast 12 weight %, ethylene/methyl acrylate copolymer having a methylacrylate content of at least 20 weight %, anhydride-modifiedethylene/methyl acrylate copolymer having a methyl acrylate content ofat least 20%, anhydride-modified ethylene/alpha-olefin copolymer, suchas an anhydride grafted LLDPE, and other modified, e.g.,anhydride-modified, olefin polymers.

[0079] Modified polymers or anhydride-modified polymers include polymersprepared by copolymerizing an unsaturated carboxylic acid (e.g., maleicacid, fumaric acid), or a derivative such as the anhydride, ester, ormetal salt of the unsaturated carboxylic acid with—or otherwiseincorporating the same into)—an olefin homopolymer or copolymer. Thus,anhydride-modified polymers have an anhydride functionality achieved bygrafting or copolymerization.

[0080] The tie layers are of sufficient thickness to provide theadherence function, as is known in the art. Each tie layer may be of asubstantially similar or a different composition and/or thickness.

Inside Layer of the Heat-Resistant Film

[0081] The inside layer 38 of the heat-resistant film 14 may provide thesurface upon which a printed image (e.g., printed information) isapplied, in which case the inside layer is preferably capable ofproviding a surface that is compatible with the selected print inksystem. Further, the inside layer 38 provides the inside surface 34 thatinterfaces with sealant film 12 and to which the sealant film 12 isdirectly laminated, i.e., inside layer 38 interfaces and bonds withoutside layer 30 of sealant film 12 as discussed in more detail below.The inside layer 38 may be a heat-resistant layer.

[0082] The inside layer 38 may include any of the thermoplastics orcompositions as discussed above in conjunction with the outside layer 30of the sealant film 12. The inside layer 38 may have a thickness of fromabout 0.025 to about 1.25 mils, such as from about 0.05 to about 0.6 milor from about 0.1 to about 0.3 mils. The thickness of the inside layer38 may range as a percentage of the total thickness of theheat-resistant film 14 of, e.g., from about 1 to 50 percent, 3 to 45percent, 5 to 40 percent, 7 to 35 percent, or 7 to 30 percent. Usefulthicknesses for the inside layer include at least about any of thefollowing values: 0.05 mil, 0.1 mil, 0.15 mil, 0.2 mil, and 0.25 mil.

Additives of Sealant and/or Heat-Resistant Films

[0083] One or more layers of the sealant and or heat-resistant films oflaminate 10 may include one or more additives useful in packaging films,such as, antiblocking agents, slip agents, antifog agents, colorants,pigments, dyes, flavorants, antimicrobial agents, meat preservatives,antioxidants, fillers, radiation stabilizers, and antistatic agents.Such additives, and their effective amounts, are known in the art.

[0084] An antifog agent may advantageously be incorporated into sealantlayer 28 or coated onto sealant layer 28, because sealant layer 28 formsthe inside surface 24 adjacent the interior of the sealed package 20.The other layers of films 12 and 14 may also contain an antifog agenttherein, e.g., when sealant layer 28 is relatively thin such that itcannot contain sufficient antifog additive to provide adequate antifogfunctionality. Suitable antifog agents may fall into classes such asesters of aliphatic alcohols, esters of polyglycol, polyethers,polyhydric alcohols, esters of polyhydric aliphatic alcohols,polyethoxylated aromatic alcohols, nonionic ethoxylates, and hydrophilicfatty acid esters. Useful antifog agents include polyoxyethylene,sorbitan monostearate, polyoxyethylene sorbitan monolaurate,polyoxyethylene monopalmitate, polyoxyethylene sorbitan tristearate,polyoxyethylene sorbitan trioleate, poly(oxypropylene), polyethoxylatedfatty alcohols, polyoxyethylated 4-nonylphenol, polyhydric alcohol,propylene diol, propylene triol, and ethylene diol, monoglyceride estersof vegetable oil or animal fat, mono- and/or diglycerides such asglycerol mono- and dioleate, glyceryl stearate, monophenylpolyethoxylate, and sorbitan monolaurate. The antifog agent isincorporated in an amount effective to enhance the antifog performanceof the laminate 10.

Cross-Linking of the Sealant and/or Heat-Resistant Films

[0085] One or more of the thermoplastic layers of the sealant and/orheat-resistant films —or at least a portion of the entire sealant and/orheat-resistant films—may be cross-linked to improve the strength of thefilm, improve the orientation of the film, and help to avoid burnthrough during heat seal operations.

[0086] Preferably, the second, heat-resistant film 14 is cross-linked toa greater degree relative to the first, sealant film 12. The higherdegree of cross-linking in second film 14 enhances the heat-resistancethereof while the lower degree of cross-linking in first film 12enhances the heat-sealability thereof. The heat-resistant film 14 ispreferably cross-linked at a dosage of at least about 40 kGy (kiloGrey)while the sealant film 12 is preferably cross-linked, if at all, at adosage of less than about 40 kGy (1 rad=0.01 Gy). For example, theheat-resistant film 14 may exposed to at least about any of thefollowing dosages: 50 kGy, 60 kGy, 70 kGy, 80 kGy, 90 kGy, 100 kGy, 110kGy, or 120 kGy. For example, a dosage ranging from about 50 to about100 kGy, such as about 60 to about 90 kGy, may be employed. For sealantfilm 12, a dosage of less than about any of the following may beemployed: 35 kGy, 30 kGy, 25 kGy, 20 kGy, 15 kGy, 10 kGy, or 5 kGy. Inmany instances, no cross-linking will be required for sealant film 12.Where cross-linking is desired, a dosage ranging from about 10 to 35kGy, such as between about 20 to 30 kGy, may be applied.

[0087] As a result of such differences in cross-linking, the second,heat-resistant film 14 preferably has a melt flow index of less thanabout 1.0 g/10 min. and the first, sealant film 12 preferably has a meltflow index of greater than about 1.0 g/10 min, as determined inaccordance with ASTM D-1238 at 230° C. and with a 21.5 KG weight. Thus,heat-resistant film 14 may have a melt flow index of less than about anyof the following: 0.9 g/10 min., 0.8 g/10 min, 0.7 g/10 min, 0.6 g/10min, 0.5 g/10 min, 0.4 g/10 min, 0.3 g/10 min, 0.2 g/10 min, or 0.1 g/10min. Sealant film 12 may have a melt flow index of greater than aboutany of the following: 5 g/10 min., 10 g/10 min., 20 g/10 min., 30 g/10min., 40 g/10 min., 50 g/10 min., 70 g/10 min., 90 g/10 min., 100 g/10min., 200 g/10 min g/10 min. 300 g/10 min., 400 g/10 min., or 500 g/10min.,

[0088] Cross-linking may be achieved by using chemical additives or bysubjecting one or more film layers to one or more energetic radiationtreatments—such as ultraviolet, X-ray, gamma ray, beta ray, and highenergy electron beam treatment—to induce cross-linking between moleculesof the irradiated material.

[0089] If desired, means other than cross-linking may be employed toachieve the differences in melt flow index between the first and secondfilms, e.g., by constructing such films from different materials.

[0090] Manufacture and Orientation of the Sealant and Heat-ResistantFilms

[0091] The first, sealant film 12 and second, heat-resistant film 14 mayeach be separately manufactured by thermoplastic film-forming processesknown in the art (e.g., tubular or blown-film extrusion, coextrusion,extrusion coating, flat or cast film extrusion). A combination of theseprocesses may also be employed.

[0092] Each of the sealant film 12 and heat-resistant film 14 may beoriented (i.e., before lamination as discussed below) or non-oriented.Either or both of the sealant film 12 and the heat-resistant film 14 maybe oriented in either the machine (i.e., longitudinal) or the transversedirection, preferably in both directions (i.e., biaxially oriented), forexample, in order to enhance the optics, strength, and durability of thefilm. Orientation of each film is also a preferred means for providingthe heat-shrinkability characteristics as discussed above. Each of thesealant and heat-resistant films may independently be oriented in atleast one direction at one of the following ratios: from about 2.5:1 toabout 8:1, from about 2.7:1 to about 6:1, from about 2.8:1 to about 5:1,from about 2.9:1 to about 4.8:1, from about 3.0:1 to about 4.6:1, orfrom about 3.2:1 to about 4.4:1.

Laminate

[0093] Laminate 10 includes sealant film 12 laminated to heat-resistantfilm 14, preferably trapping the printed image 16 between the sealantand heat-resistant films. Preferably, at least one of the inside sealantfilm 12 and/or the outside heat-resistant film 14 are heat-shrinkable asdiscussed above so that the resulting laminate 10 presents a superiorappearance upon sealing to the support member 18 (as described below).

[0094] When laminate 10 is used for poultry packaging, it preferably hasa gas transmission rate greater than about 3000 cubic centimeters persquare meter per day per 1 atmosphere of gas pressure differentialmeasured at 0% relative humidity and 23° C., such as at least about3500, 4000, 4500, 5000, 5500, 6000, or 6500 cubic centimeters per squaremeter per day per 1 atmosphere of gas pressure differential measured at0% relative humidity and 23° C.

[0095] Laminate 10 preferably has a has a free shrink in at least onedirection (i.e., machine or transverse direction) or in at least each oftwo directions (machine and transverse directions), measured at 185° F.,of at least about 10%, such as at least about 15%, 20%, 25%, 30%, 40%,50%, 55%, 60%, or 65%. Further, the laminate may have a free shrink inat least one direction (machine or transverse direction) or in at leasteach of two directions (machine and transverse directions) of at leastabout any of the foregoing shrink values when measured at any of 185°F., 190° F., 200° F., or 210° F. This may be achieved by selecting atleast one of the first and second films 12 and/or 14 to have a freeshrink at 185° F. in at least one direction of at least about 10%, asdescribed above with respect to each film. If desired, only one of films12 or 14 may have such free shrink functionality; the other may haveless heat-shrinkability or no heat-shrinkability.

[0096] The thickness of the laminate may be less than about any of thefollowing values: 5, 4, 3, 2.5, 2.4, 2.3, 2.2, 2.1, 2, 1.9, 1.8, 1.7,1.5, 1.25, and 1.0 mils.

Trap Printed Image

[0097] A printed image 16 is preferably disposed (i.e., trap printed)between the sealant and heat-resistant films at the interface betweenthe outside surface 26 of sealant film 12 and the inside surface 34 ofthe heat-resistant film 14. This may be accomplished by printing one ormore images 16 on one or both of these surfaces before laminating thefilms together, so that upon lamination the printed images 16 are“trapped” between the two films. For example, the printed image may be“reverse trap printed” by printing the image onto surface 34 of theheat-resistant film.

[0098] As discussed below, heat-resistant film 14 is preferablytransparent so that the trapped image 16 is visible therethrough inorder to provide information to the retail purchaser of the package.Accordingly, package 10 may be provided with consumer-specificinformation at the time of packaging at a centralized packagingfacility, in the form of a printed image trapped within the laminate 10used at part of the sealed package 20. The availability of trap printedinformation in laminate 10 reduces and potentially eliminates the needfor additional package printing or labeling at the retail distributionpoint. The printed image 16 may include indicia such as productinformation, nutritional information, source identification, and otherinformation, as discussed above.

[0099] To form the printed image, one or more layers of ink are printedonto the print surface. The ink is selected to have acceptable inkadhesion, appearance, and heat resistance once printed on the film. Thefilm may be printed by any suitable method, such as rotary screen,gravure, or flexographic techniques. Inks and processes for printing onplastic films are known to those of skill in the art. See, for example,Leach & Pierce, The Printing Ink Manual, (5^(th) ed., Kluwer AcademicPublishers, 1993), which is incorporated herein in its entirety byreference.

[0100] To improve the adhesion of the ink to the surface of the sealantor heat-resistant film, the surface of the sealant or heat-resistantfilm may be treated or modified before printing. Surface treatments andmodifications include: i) mechanical treatments, such as coronatreatment, plasma treatment, and flame treatment, and ii) primertreatment. Surface treatments and modifications are known to those ofskill in the art. The flame treatment is less desirable for aheat-shrinkable film, since heat may prematurely shrink the film. Theink system should be capable of withstanding without diminishedperformance the temperature ranges to which it will be exposed duringlamination, heat sealing, packaging, and end use.

[0101] If a trap-printed image 16 is not necessary or desired for theparticular packaging application in which the laminate will be used,e.g., where no image is desired or where a surface-printed image willsuffice, the second, heat-resistant film 14 may be omitted. In such analternative embodiment, the lid would not be a laminate but wouldcomprise only the sealant film 12. In this event, the outside layer 30of sealant film 12 preferably has a heat-resistant composition andfunctionality similar to that described above with respect to outsidelayer 40 of second film 14.

Appearance Characteristics of the Laminate

[0102] Each of laminate 10 and heat-resistant film 14 preferably has lowhaze characteristics. Haze is a measurement of the transmitted lightscattered more than 2.5° from the axis of the incident light. Haze ismeasured against the outside surface 36 of the heat-resistant layer 40of second film 14, according to the method of ASTM D 1003-95. Allreferences to “haze” values in this application are by this standard.Preferably, the haze of either laminate 10 or heat-resistant film 14 isno more than about (in ascending order of preference) 20%, 15%, 10%, 9%,8%, or 7%.

[0103] Laminate 10 preferably has a gloss, as measured against theoutside surface 36 of the heat-resistant layer 40 of at least about (inascending order of preference) 40%, 50%, 60%, 63%, 65%, 70%, 75%, or80%. These percentages represent the ratio of light reflected from thesample to the original amount of light striking the sample at thedesignated angle. All references to “gloss” values in this applicationare in accordance with ASTM D 2457-90 (45° angle).

[0104] Preferably, laminate 10 is substantially transparent (at least inthe non-printed regions) so that the packaged food item 22 is visiblethrough the laminate. “Transparent” as used herein means that thematerial transmits incident light with negligible scattering and littleabsorption, enabling objects (e.g., packaged food or print) to be seenclearly through the material under typical unaided viewing conditions(i.e., the expected use conditions of the material). If laminate 10 istransparent then both heat-resistant film 14 and sealant film 12 arealso transparent. Optionally, heat-resistant film 14 may be transparentwhile sealant film is opaque, in which case laminate 10 is opaque whiletrap print 16 is still clearly visible through heat-resistant film 14.Preferably, the clarity of any of the laminate 10, sealant film 12, andheat-resistant film 14 are at least about any of the following values:45%, 50%, 55%, and 60%, as measured in accordance with ASTM D1746-92.Similarly, the transmittance of laminate 10 is preferably at least about60%, 65%, 70%, 75%, 80%, 85%, or 90%, as measured in accordance withASTM

Manufacture of the Laminate

[0105] To manufacture laminate 10, the outside surface 26 of the sealantfilm 12 is placed adjacent to or in contact with the inside surface 34of heat-resistant film 14 so that the films may be bonded together by asuitable lamination technique. Suitable lamination techniques are knownin the art, and include adhesive bonding, reactive surface modification(e.g., corona treatment, flame treatment, or plasma treatment), heattreatment, pressure treatment, heat-welding, and combinations thereof.Suitable lamination methods are described in U.S. Pat. No. 5,779,050issued Jul. 14, 1998 to Kocher et al entitled “Lidded Package Having aTab to Facilitate Peeling,” which is incorporated herein in its entiretyby reference.

[0106] Heat-resistant film 14 may be directly laminated to sealant film12. The term “directly laminated” as used herein means that a first filmis bonded to a second film by a suitable lamination method without anadditional film between the first and second films. The first film(e.g., sealant film) may be considered as “directly laminated” to thesecond film (e.g., heat-resistant film)—even if additional material ispresent between the first and second films—if the additional material ispresent primarily to facilitate the lamination of the first and secondfilms (e.g., an adhesive used in adhesive lamination) or to form part ofthe trap print (e.g., a printed image) between the first and secondfilms.

[0107] As a reactive surface modification lamination method, coronatreatment may be combined with pressure and, optionally, heatimmediately after the corona treatment. The corona treatment providesthe film with a reactively modified surface to enhance laminationbonding. The amount of corona discharge to which the films are exposedis directly proportional to the amount of power supplied to the coronatreatment units, and also indirectly proportional to the speed at whichthe films are passed through the units. In general, corona treatmentunits operate by passing a high voltage electrical current through anelectrode positioned adjacent a film surface to be treated. Theelectrode then produces an electrical discharge which ionizes thesurrounding air to cause reactive surface modification, e.g., oxidation,of the treated film surface.

[0108] Any desired combination of power input to the corona unit andfilm speed may be employed to achieve a desired bond-strength betweenthe films. The amount of power supplied to the corona treatment unitsmay range, for example, from about 0.02 to about 0.5 kilowatts (kw) perinch of film width. The film speed through the corona treatment unit mayrange, for example, from about 10 to about 2000 feet/minute.

Sealed Package

[0109] The lidstock laminate 10 may be heat sealed to support member 18to form sealed package 20.

Support Member

[0110] Support member 18 is a component of package 20 in addition tolaminate 10. Product 22 (e.g., a poultry or other food product) may bedisposed on or in support member 18. For example, poultry products maybe disposed in a tray-like support member comprising, for example,expanded polystyrene sheet material that has been thermoformed into adesired shape for supporting the poultry product. Product support member18 preferably is in the form of a tray having side walls 50 and base52—which define cavity 46 into which the product 22 may be disposed. Aperipheral flange 48 preferably extends from side walls 50 to provide asealing surface for attachment of lid 10 to the support member 18 toenclose the product 22 within the cavity 46.

[0111] Although the drawings show support member 18 in oneconfiguration, support member 18 may have any desired configuration orshape, such as rectangular, round, or oval. The support member may besubstantially rigid, semi-rigid, or flexible.

[0112] Flange 48 may also have any desired shape or design, such as thesubstantially flat design presenting a single sealing surface as shownin the drawings, or a more elaborate design which presents two or moresealing surfaces, such as the flange configurations disclosed in U.S.Pat. Nos. 5,348,752 and 5,439,132, the disclosures of which areincorporated herein by reference.

[0113] Support member 18 may be formed from any material useful for theexpected end use conditions, including polyvinyl chloride, polyethyleneterephthalate, polystyrene, polyolefins (e.g., high density polyethyleneor polypropylene), paper pulp, nylon, and polyurethane. The supportmember may be foamed or non-foamed as desired. Preferably support member18 is permeable to the passage of gas therethrough, particularly whenproduct 22 is a poultry product. When poultry products are to bepackaged in package 20, support member 18 preferably has a thickness andcomposition sufficient to provide a gas transmission rate of at leastabout (in ascending order of preference) 1000, 1500, 2000, 2500, 3000 or3500 cubic centimeters per square meter per day per 1 atmosphere of gaspressure differential measured at 0% relative humidity and 23° C.Preferably, support member 18 comprises foamed polystyrene. Suitablepolystyrenes include polystyrene homopolymer, high impact polystyrene(HIPS), styrene/butadiene copolymer, styrene/maleic anhydride copolymer(SMA), polyphenylene oxide (PPO), and blends thereof. More preferably,the support member consists essentially of foamed polystyrene, i.e.,without any liners on the inner/upper surface 54 or outer surface 56.Such a support member is less expensive to manufacture and provides ahigher gas transmission rate than a lined support member. When lidded bylaminate 10 in accordance with the present invention, which formshermetic yet peelable seal with peripheral flange 48 of support member18, the resultant package 20 is highly advantageous for the packaging ofpoultry products.

Manufacture of the Sealed Package

[0114] To make sealed package 20, the item to be packaged (e.g., product22) is placed onto support member 18. Laminate 10 is then placed overthe support member so that the sealant film 12 of the laminate contactsthe support member 18. Laminate 10 may be supplied from a larger web ofthe laminate, for example, from a roll that is unwound to supplylaminate as needed.

[0115] A heated bar or other heated member engages the outside surface36 of laminate 10, typically in the form of a closed geometrical shapecorresponding to the shape of the peripheral flange 48 of the supportmember, to compress the laminate against the flange of the supportmember. The resulting heat transfer and compression causes the sealantlayer 28 of the laminate and the upper surface 54 of the support memberin the area of flange 48 to soften and intermix with one another. Theheating bar is removed to allow the sealed area to cool and form asealed bond, i.e., heat-seal 44. The excess lid material extendingbeyond the flange may be trimmed by a cutting operation. Further, if thelaminate is supplied from a roll, portions may be severed from the webbefore, after, or simultaneously with the heat-welding of the laminateto support member 18. Laminate 10 may be severed by a conventionalcutting device (e.g., a sharp cutting instrument or a thermal cuttingdevice such as a heated wire or heated blade). A representative processfor heat sealing a lid to a support member is described in U.S. Pat. No.5,779,050 to Kocher, which was previously incorporated by reference.

[0116] The resulting heat-weld or heat-seal 44 preferably extendscontinuously around the upper surface of flange 48 to hermetically sealor enclose product 22 within package 20. In this manner, laminate 10 andsupport member 18 preferably form a substantially gas-permeableenclosure for product 22 to protect it from contact with the surroundingenvironment, including dirt, dust, moisture, and microbial contaminates.At the same time, the gas-permeability of the package 20 allows apackaged poultry product 22 to gradually expel hydrogen sulfide gasbetween the time that the product is packaged and the time when aconsumer opens the package, thereby preventing an accumulation of thegas in the package so that the consumer is not subjected to a suddenrelease of the accumulated gas when he or she opens the package.

[0117] The sealing of the laminate 10 to support member 18 may be by oneor more heat sealing methods, including thermal conductance sealing (asdescribed above), impulse sealing, ultrasonic sealing, and dielectricsealing. As a result of the above-described heat-shrinkability of thefirst film 12 and/or second film 14, such heat sealing causes laminate10 to heat-contract while restrained by heat seal 44, thereby renderingthe laminate, as lidded on support member 18, in a tensioned state witha tight, aesthetically-pleasing appearance.

[0118] Product 22 is shown as a “high profile” product—that is, aproduct having a maximum height that is above the maximum height ofsupport member 18 (i.e., the level at which flange 48 is located) suchthat the portion of the product that extends above the level of flange48 will be in contact with lid 10. However, a “low profile” product—thatis, a product having a maximum height that is below the maximum heightof support member 18—may also be packaged in accordance with the presentinvention. When a high profile configuration is employed, thelaminate/lid 10 is preferably in tensioned contact with the portion ofthe product that extends above the flange, e.g., as a result of being ina heat-contracted state as discussed above.

Seal Strength

[0119] As noted above, the first, sealant film 12 is capable of bondingdirectly to a surface comprising foamed polystyrene at a bond strengthranging from about 0.5 to about 5.0 lb_(f) per inch. Accordingly, whensupport member 18 comprises foamed polystyrene and is non-lined, thebond strength of heat-seal 44 ranges from about 0.5 to about 5.0 lb_(f)per inch. It has been found that a peel strength falling within suchrange advantageously provides a seal that is both hermetic, i.e.,protects product 22 from contact with the surrounding environment, andalso peelable, i.e., readily openable by a consumer. The bond strengthof such heat seal may be determined in accordance with ASTM D882-97 as ameasurement of the amount of force required to separate the sealantlayer of the laminate from the support member to which the sealant layerhas been sealed, e.g., by using an Instron tensile tester with crossheadspeed is 20 inches per minute, with at least three, 1-inch wide,representative samples of the laminate 10 heat-sealed to flange 48.

[0120] The following examples are presented for the purpose of furtherillustrating and explaining the present invention and are not to betaken as limiting in any regard.

EXAMPLES

[0121] In the examples below, the following materials were used:

[0122] RAW MATL: “LLDPE1”

[0123] TRADE NAME: ATTANE 4203

[0124] SUPPLIER: DOW

[0125] GENERIC NAME: RESIN-POLYETHYLENE, LINEAR LOW DENSITY

[0126] CHEMICAL NATURE: ETHYLENE/OCTENE COPOLYMER

[0127] KEY PROPERTIES: MF 0.80; D-0.905; MP 123 DEGREES C; 11.5% OCTENE

[0128] RAW MATL: “AF”

[0129] TRADE NAME: ATMOS 300K SPECIAL

[0130] SUPPLIER: CROMPTON (FORMERLY WITCO)

[0131] GENERIC NAME: ANTIFOG AGENT

[0132] CHEMICAL NATURE: 88% MONO- & DIGLYCERIDES/12% PROPYLENE GLYCOL

[0133] KEY PROPERTIES: SP.GR. 0.96; FLASH POINT 300 DEGREES F.

[0134] RAW MATL: “EVA”

[0135] TRADE NAME: ESCORENE LD-720.92 RESIN

[0136] SUPPLIER: EXXON

[0137] GENERIC NAME: RESIN-EVA

[0138] CHEMICAL NATURE: ETHYLENE/VINYL ACETATE COPOLYMER

[0139] KEY PROPERTIES: VA 19.3%; MI 1.5; DENSITY 0.940

[0140] RAW MATL: “SBC1”

[0141] TRADE NAME: STYROLUX 684D

[0142] SUPPLIER: BASF

[0143] GENERIC NAME: RESIN-THERMOPLASTIC RUBBER

[0144] CHEMICAL NATURE: STYRENE BUTADIENE BLOCK COPOLYMER

[0145] KEY PROPERTIES: 76% STYRENE/24% 1,3 BUTADIENE; MI 11; DENSITY1.01

[0146] RAW MATL: “SBC2”

[0147] TRADE NAME: KRATON D-1401P

[0148] SUPPLIER: SHELL

[0149] GENERIC NAME: RESIN-THERMOPLASTIC RUBBER

[0150] CHEMICAL NATURE: STYRENE BUTADIENE COPOLYMER

[0151] KEY PROPERTIES: 75% STYRENE/25% BUTADIENE; MI 11; DENSITY 1.01

[0152] RAW MATL: “LLDPE2”

[0153] TRADE NAME: DOWLEX 3010

[0154] SUPPLIER: DOW

[0155] GENERIC NAME: RESIN-POLYETHYLENE, LINEAR LOW DENSITY

[0156] CHEMICAL NATURE: ETHYLENE/OCTENE COPOLYMER

[0157] KEY PROPERTIES: MF 4.6-6.2; DENSITY 0.921; MP 125 DEGREES C.

[0158] RAW MATL: “AB”

[0159] TRADE NAME: KAOPOLITE SF

[0160] SUPPLIER: KAOPOLITE, INC.

[0161] GENERIC NAME: ANTIBLOCK

[0162] CHEMICAL NATURE: ANHYDROUS ALUMINUM SILICATE

[0163] KEY PROPERTIES: SP. GR. 2.63

[0164] RAW MATL: “PEC”

[0165] TRADE NAME: ESCORENE PD-9302 E1

[0166] SUPPLIER: EXXON

[0167] GENERIC NAME: RESIN-PROPYLENE/ETHYLENE

[0168] CHEMICAL NATURE: PROPYLENE/ETHYLENE COPOLYMER

[0169] KEY PROPERTIES: MP 139 DEGREES C.; MF 3.1-3.9; 3.3% ETHYLENE

Example 1

[0170] A trap-printed laminate having the composition and constructionshown in Table 1 was formed by laminating a First (sealant) Film, havinga printed image on its Fifth (outside, interface) layer, to a SecondFilm via corona treatment bonding by corona-treating the surface layerof each film that forms the lamination interface (Fifth layer of FirstFilm and First layer of Second Film) and pressing the films togethersuch that the treated surfaces contact and bond with one another. TheExample 1 laminate had a total thickness of 1.3 mils and a gastransmission rate of 5700 cc/m²-day-atm. (0% RH, 73° F.). The First Filmwas biaxially oriented and had a free shrink measured at 185° F. of 32%in the machine direction and 36% in the transverse direction, athickness of 0.650 mils, and a melt flow index of 17.9 g/10 min. TheFirst Film was irradiated with electron-beam radiation at a dosage of 30kGy. The Second (heat-resistant) Film was biaxially oriented and had afree shrink measured, at 185° F. of 29% in the machine direction and 26%in the transverse direction, a thickness of 0.650 mils, and a melt flowindex of 0.3 g/10 min. The Second Film was irradiated with electron-beamradiation at a dosage of 75 kGy. TABLE 1 Film Layer Designation LayerComposition Thickness Ratio of Designation (Function) (weight %)Layer/Total Film First First (inside, sealant layer) 97% SBC20.146/0.650 (Sealant) 3% AF Film Second (tie layer) 96% EVA 0.049/0.6504% AF Third (bulk, core) 96% LLDPE1 0.259/0.650 4% AF Fourth (tie layer)96% EVA 0.049/0.650 4% AF Fifth (outside, interface layer) 96% SBC10.147/0.650 [Printed Image] 4% AF Lamination Interface Second First(inside, interface layer) 94% LLDPE2 0.078/0.650 (Heat- 4% AFResisistant) 2% AB Film Second 96% LLDPE1 0.098/0.650 4% AF Third 96%EVA 0.048/0.650 4% AF Fourth (bulk, core) 96% SBC1 0.203/0.650 4% AFFifth 96% EVA 0.048/0.650 4% AF Sixth 96% LLDPE1 0.097/0.650 4% AFSeventh (outside, abuse) 94% LLDPE2 0.078/0.650 4% AF 2% AB

Example 2

[0171] A trap-printed laminate having the composition and constructionshown in Table 2 was formed by laminating a First (sealant) Film, havinga printed image on its Fifth (outside, interface) layer, to a SecondFilm via corona treatment bonding by corona-treating the surface layerof each film that forms the lamination interface (Fifth layer of FirstFilm and First layer of Second Film) and pressing the films togethersuch that the treated surfaces contact and bond with one another. TheExample 2 laminate had a total thickness of 1.3 mils and a gastransmission rate of 5600 cc/m²-day-atm. (0% RH, 73° F.). The First Filmwas biaxially oriented and had a free shrink measured at 185° F. of 30%in the machine direction and 33% in the transverse direction, athickness of 0.650 mils, and a melt flow index of 16.55 g/10 min. TheFirst Film was irradiated with electron-beam radiation at a dosage of 30kGy. The Second (heat-resistant) Film was biaxially oriented and had afree shrink measured at 185° F. of 29% in the machine direction and 26%in the transverse direction, a thickness of 0.650 mils, and a melt flowindex of 0.3 g/10 min. The Second Film was irradiated with electron-beamradiation at a dosage of 75 kGy. TABLE 2 Film Layer Designation LayerComposition Thickness Ratio of Designation (Function) (weight %)Layer/Total Film First First (inside, sealant layer) 97% SBC20.143/0.650 (Sealant) 3% AF Film Second (tie layer) 96% EVA 0.054/0.6504% AF Third (bulk, core) 96% LLDPE1 0.254/0.650 4% AF Fourth (tie layer)96% EVA 0.052/0.650 4% AF Fifth (outside, interface layer) 97% SBC20.147/0.650 [Printed Image] 3% AF Lamination Interface Second First(inside, interface layer) 94% LLDPE2 0.078/0.650 (Heat- 4% AF Resistant)2% AB Film Second 96% LLDPE1 0.098/0.650 4% AF Third 96% EVA 0.048/0.6504% AF Fourth (bulk, core) 96% SBC1 0.203/0.650 4% AF Fifth 96% EVA0.048/0.650 4% AF Sixth 96% LLDPE1 0.097/0.650 4% AF Seventh (outside,abuse) 94% LLDPE2 0.078/0.650 4% AF 2% AB

Example 3

[0172] A trap-printed laminate having the composition and constructionshown in Table 3 was formed by laminating a First (sealant) Film, havinga printed image on its Fifth (outside, interface) layer, to a SecondFilm via corona treatment bonding by corona-treating the surface layerof each film that forms the lamination interface (Fifth layer of FirstFilm and First layer of Second Film) and pressing the films togethersuch that the treated surfaces contact and bond with one another. TheExample 3 laminate had a total thickness of 1.3 mils and a gastransmission rate of 5200 cc/m²-day-atm. (0% RH, 73° F.). The First Filmwas biaxially oriented and had a free shrink measured at 185° F. of 27%in the machine direction and 25% in the transverse direction, athickness of 0.650 mils, and a melt flow index of 32.3 g/10 min. TheFirst Film was irradiated with electron-beam radiation at a dosage of 30kGy. The Second (heat-resistant) Film was biaxially oriented and had afree shrink measured at 185° F. of 29% in the machine direction and 26%in the transverse direction, a thickness of 0.650 mils, and a melt flowindex of 0.3 g/10 min. The Second Film was irradiated with electron-beamradiation at a dosage of 75 kGy. TABLE 3 Film Layer Designation LayerComposition Thickness Ratio of Designation (Function) (weight %)Layer/Total Film First First (inside, sealant layer) 97% SBC20.143/0.650 (Sealant) 3% AF Film Second (tie layer) 96% EVA 0.057/0.6504% AF Third (bulk, core) 96% SBC1 0.226/0.650 4% AF Fourth (tie layer)96% EVA 0.061/0.650 4% AF Fifth (outside, interface layer) 94% LLDPE20.163/0.650 [Printed Image] 4% AF 2% AB Lamination Interface SecondFirst (inside, interface layer) 94% LLDPE2 0.078/0.650 (Heat- 4% AFResistant) 2% AB Film Second 96% LLDPE1 0.098/0.650 4% AF Third 96% EVA0.048/0.650 4% AF Fourth (bulk, core) 96% SBC1 0.203/0.650 4% AF Fifth96% EVA 0.048/0.650 4% AF Sixth 96% LLDPE1 0.097/0.650 4% AF Seventh(outside, abuse) 94% LLDPE2 0.078/0.650 4% AF 2% AB

Example 4

[0173] The laminates of Examples 1-3 were each sealed to the flange of apolystyrene foam tray to form a lid for the tray. The trays were CD-92meat trays commercially available from the Cryovac Division of SealedAir Corporation, and had no sealant liner on the flange of the trays.Thus, the laminates were sealed directly to the foamed surface of thetray flange. Sealing was accomplished by placing the laminates over thetray, with the First Layer of the First Film in contact with the flange.A heat seal was formed between the First Layer and the flange using a‘hot bar’-type lidding apparatus from Ross Industries. The hot sealingbar was maintained at a temperature of 290° F. and applied a contactpressure to each laminate and flange of 80 psi with a 1 second dwelltime.

[0174] After the laminates were sealed to the trays, six (6) 1-inch widestrips of the flange with the laminate sealed thereto were cut from eachtray, in both the length and width dimensions of the trays. The stripswere used to measure the bond-strength between the laminate and thefoamed flange using an Instron tensile tester with a crosshead speed of20 inches per minute. The maximum amount of force required to cause aseparation of the bond between the laminate and the foam was measured inaccordance with ASTM D882-97. The results were averaged for each of thesix samples in both the length and width dimension for each sealedlaminate/tray. The results are reported in Table 4. TABLE 4 BondStrength (lb_(f)/inch) Laminate Width Length Example 1 1.92 1.06 Example2 2.1 1.16 Example 3 1.76 1.04

[0175] Each of Examples 1-3 exhibited a bond-strength to polystyrenefoam that fell within the desired range of 0.5 to 5.0 lb_(f)/inch.

Example 5

[0176] The laminates of Examples 1 and 3 were tested for the followingoptical properties: haze (ASTM D-1003-00), gloss (ASTM D-2457-97),transmittance (ASTM D-1003-00), and clarity (ASTM D-1746-97). Theresults are summarized in Table 5. TABLE 5 Laminate Haze (%) Gloss (%)Transmittance (%) Clarity (%) Example 1 6.1 80 94.2 61.8 Example 3 6.680 93.6 61.8

[0177] Such optical properties are suitable for commercial packagingapplications.

[0178] The above descriptions are those of preferred embodiments of theinvention. Various alterations and changes can be made without departingfrom the spirit and broader aspects of the invention as defined in theclaims, which are to be interpreted in accordance with the principles ofpatent law, including the doctrine of equivalents. All parts andpercentages are by weight, unless otherwise indicated or well understoodin the art. Except in the claims and the specific examples, or whereotherwise expressly indicated, all numerical quantities in thisdescription indicating amounts of material, reaction conditions, useconditions, molecular weights, and/or number of carbon atoms, and thelike, are to be understood as modified by the word “about” in describingthe broadest scope of the invention. Any reference to an item in thedisclosure or to an element in the claim in the singular using thearticles “a,” “an,” “the,” or “said” is not to be construed as limitingthe item or element to the singular unless expressly so stated. EachASTM test reference and method referred to in this application isincorporated herein in its entirety by reference.

What is claimed is:
 1. A laminate, comprising: a. a first film capableof bonding directly to a surface comprising foamed polystyrene at a bondstrength ranging from about 0.5 to about 5.0 lb_(f) per inch; b. asecond film bonded to the first film; and c. a printed image trappedbetween the first and second films, wherein: at least one of the firstand second films has a free shrink at 185° F. in at least one directionof at least about 10%, and the laminate has a gas transmission rategreater than about 3000 cubic centimeters per square meter per day per 1atmosphere of gas pressure differential measured at 0% relative humidityand 23° C.
 2. The laminate of claim 1, wherein the second film iscross-linked to a greater degree relative to the first film.
 3. Thelaminate of claim 1, wherein the second film has a melt flow index ofless than about 1.0 g/10 min. and the first film has a melt flow indexof greater than about 1.0 g/10 min.
 4. The laminate of claim 1, whereinthe laminate has a clarity of at least about 45%.
 5. The laminate ofclaim 1, wherein the second film has a haze of no more than about 20%,measured against an outer surface of the second film.
 6. A package,comprising: a. a product support member for supporting a productthereon, the support member comprising foamed polystyrene; and b. alaminate, comprising a first film and a second film bonded together witha printed image trapped therebetween, wherein: at least one of the firstand second films has a free shrink at 185° F. in at least one directionof at least about 10%, the laminate has a gas transmission rate greaterthan about 3000 cubic centimeters per square meter per day per 1atmosphere of gas pressure differential measured at 0% relative humidityand 23° C., and the first film is bonded to the support member in theform of a peelable, hermetic seal that extends around the product toenclose the product between the laminate and support member, the sealhaving a bond strength ranging from about 0.5 to about 5.0 lb_(f) perinch.
 7. The package of claim 6, wherein: the support member has anupper surface consisting essentially of foamed polystyrene, and thefirst film is bonded directly to the upper surface of the supportmember.
 8. The package of claim 7, wherein the bond between the firstfilm and support member is a heat-seal.
 9. The package of claim 6,wherein the laminate is heat-contracted.
 10. The package of claim 6,wherein the laminate is in tensioned contact with at least a portion ofthe product.
 11. The package of claim 10, wherein the laminate isheat-contracted.
 12. The package of claim 6, wherein the second film iscross-linked to a greater degree relative to the first film.
 13. Thepackage of claim 6, wherein the second film has a melt flow index ofless than about 1.0 g/10 min. and the first film has a melt flow indexof greater than about 1.0 g/10 min.
 14. The package of claim 6, whereinthe laminate has a clarity of at least about 45%.
 15. The package ofclaim 6, wherein the second film has a haze of no more than about 20%,measured against an outer surface of the second film.
 16. A package,comprising: a. a product support member for supporting a productthereon, the support member having an upper surface consistingessentially of foamed polystyrene; and b. a film bonded directly to theupper surface of the support member in the form of a peelable, hermeticseal that extends around the product to enclose the product between thefilm and support member, the seal having a bond strength ranging fromabout 0.5 to about 5.0 lb_(f) per inch, the film having a free shrink at185° F. in at least one direction of at least about 10% and a gastransmission rate greater than about 3000 cubic centimeters per squaremeter per day per 1 atmosphere of gas pressure differential measured at0% relative humidity and 23° C.
 17. The package of claim 16, wherein thebond between the film and support member is a heat-seal.
 18. The packageof claim 16, wherein the film is heat-contracted.
 19. The package ofclaim 16, wherein the film is in tensioned contact with at least aportion of the product.
 20. A package, comprising: a. a product supportmember for supporting a product thereon; and b. a laminate, comprising afirst film and a second film bonded together, wherein: the first film isbonded to a surface of the support member in the form of a peripheralseal that extends around the product to enclose the product between thefilm and support member, and the second film is cross-linked to agreater degree relative to the first film such that the second film hasa melt flow index of less than about 1.0 g/10 min. and the first filmhas a melt flow index of greater than about 1.0 g/10 min.
 21. Thepackage of claim 20, wherein the bond between the first film and supportmember is a heat-seal.
 22. The package of claim 20, wherein: the supportmember has an upper surface consisting essentially of foamedpolystyrene; and the first film is bonded directly to the upper surfaceof the support member.
 23. The package of claim 22, wherein the bondbetween the first film and support member is a peelable, hermetic sealhaving a bond strength ranging from about 0.5 to about 5.0 lb_(f) perinch.
 24. The package of claim 20, wherein at least one of the first andsecond films has a free shrink at 185° F. in at least one direction ofat least about 10%.
 25. The package of claim 20, wherein the laminatehas a gas transmission rate greater than about 3000 cubic centimetersper square meter per day per 1 atmosphere of gas pressure differentialmeasured at 0% relative humidity and 23° C.
 26. The package of claim 20,further including a printed image trapped between the first and secondfilms.